UNITED NATIONS -- One of the largest humanitarian relief efforts ever attempted is now mobilizing to help Pakistan cope with what its government and U.N. agencies are calling the worst natural disaster in modern memory.

The death toll is much smaller than in past disasters: About 1,600 are believed dead so far. But experts say initial assessments show the scale of damage and human suffering left by torrential monsoon rains over the past three weeks dwarfs the 2004 Indian
Ocean tsunami, 2005 Kashmir earthquake, 2008 Cyclone Nargis disaster in Burma, and Jan. 12 earthquake in Haiti -- combined.

"What we face in Pakistan today is a natural calamity of unprecedented proportions," Pakistan's foreign minister, Makhdoom Shah Mahmood Qureshi, said during a special U.N. session to address the crisis, held here yesterday. "These
are the worst monsoon floods in living memory."

Debate is heating up over what caused the catastrophe, with experts pointing to deforestation, intensive land-use practices or mismanagement of the Indus River as possible causes. But top U.N. and Pakistani government officials are now clearly pointing
to climate change as the principal culprit.

"Climate change, with all its severity and unpredictability, has become a reality for 170 million Pakistanis," said Qureshi in his appeal for aid. "The present situation in Pakistan reconfirms our extreme vulnerability to the adverse impacts
of climate change."

Both Qureshi and U.N. Secretary-General Ban Ki-moon hinted that they would use the Pakistan crisis to spur the now-stalled international climate talks. At the very least, the disaster shows that massive funding is needed to make the developing world more
resilient to extreme weather events, Ban said.

"Ultimately, we must recognize that climate change will bring more incidents of extreme weather; that is why we must invest more in reducing the risk of future disasters," he said.

Clinton pledges $150 million, seeks private help

Meanwhile, the focus lies squarely on the humanitarian response in Pakistan.

Yesterday, Secretary of State Hillary Rodham Clinton told government leaders gathered here that the United States would contribute $150 million of the $459 million the United Nations says is needed to finance a 90-day emergency period. She also urged
corporations and private citizens to donate money online to the Department of State's Pakistan Relief Fund or to give
small $10 donations through their mobile phones by sending the text message "flood" to the number 27722.

Clinton added that so far, the U.S. military has distributed more than 400,000 meals from storehouses in Dubai, United Arab Emirates, on top of 1 million pounds of supplies, including enough shelter material for 100,000 people. At the same time, the World
Food Programme says it has distributed enough food rations to meet the needs of more than a million people for one month.

U.K. head of international development Andrew Mitchell said his government would contribute $100 million to relief efforts. An additional $25 million has been raised from private donors in the United Kingdom, he said. Germany has committed €25
million for flood relief.

The response from Muslim nations has been slower but is now building up. Saudi Arabia has told Pakistan that it would contribute relief in excess of $100 million.

Thus far, about 60 percent of the United Nations' $459 million funding appeal has been met. Billions of dollars more will be needed in the long run "to help Pakistan meet the immediacy of this crisis and then help them recover from it,"
Clinton said.

Estimated losses are immense.

Aid coordinators in Islamabad say between 15 million and 20 million people have been hit, losing their homes, livelihoods or access to basic needs like sanitation, health care, food and potable water.

Qureshi said eruptions of violence and rioting over food shortages couldn't be ruled out.

Impending food and disease crises

"A food crisis is also possible if food assistance is not reached soon enough," warned Martin Mogwanja, the United Nations' chief humanitarian relief coordinator in Pakistan. "And if [aid is] not provided soon enough, there could be
a second wave of death caused by waterborne diseases such as gastroenteritis and acute waterborne disease," he told reporters in a teleconference yesterday.

Officials say about 800,000 to 900,000 homes have been destroyed or made unlivable. The government believes 4.6 million have been left homeless in just two provinces, Punjab and Sindh.

Areas in the country's north and northwest have been hardest hit, especially Khyber Pakhtunkhwa province, where several communities have been cut off from the outside world after floodwaters washed out key bridges. About 70 percent of bridges and
roads have been destroyed here, officials report. Pakistan's government says little transportation infrastructure remains in the Swat valley, the scene of intense fighting between the army and Islamic insurgents
in 2009.

Pakistan's agricultural economy, the source of income for about 70 percent of the population, has borne the brunt of the damage. "This is where we have been hit the most," said Qureshi.

More than 17 million acres of farmland was inundated, Qureshi said. U.N. officials figure that more than 200,000 head of livestock have been killed in the flooding. And the nation's cotton crop, an important source of export earnings, has largely
been wiped out after 1 million acres of the crop was lost to floods in Punjab.

The flood disaster could also exacerbate global food prices, in particular wheat. The government of Pakistan says the season's harvest is pretty much gone and 1 million metric tons of wheat that was sitting in storage is now gone. Droughts in Russia,
Australia and Canada had already sent wheat prices soaring in recent weeks.

Following the emergency period, the government's next goal is to rebuild the nation's farm economy. Qureshi and others estimate that at least $2 billion will be needed to cover losses to agriculture alone.

Further flood damage expected

Officials are so far refusing to estimate what a larger recovery effort will cost once immediate needs are met, but all agree that the price tag will be tremendous.

The World Bank says it will extend to Pakistan $900 million in loans to meet the broader rebuilding effort. Meanwhile, the government, World Bank and Asian Development Bank are launching a "damage needs assessment" that may not be complete until
the end of October.

Officials in Islamabad also say that they will set up an independent body to manage rebuilding funds, hoping to skirt concerns that aid dollars will be lost to corruption. Qureshi promised that relief spending would be fully transparent.

The government is also disputing media suggestions that Taliban fighters and Islamic radicals are taking advantage of the crisis and delivering relief assistance more effectively. Still, Qureshi acknowledged to the press that increased activity by militants
was a concern.

Ban said he is considering holding a special donors' conference at U.N. headquarters in New York in September, when hundreds of world leaders will gather for the annual opening of the General Assembly.

Recovery efforts from disasters of smaller scale have typically come with giant price tags. Most experts say some $10 billion will be needed to help Haiti recover from the devastating January earthquake over the next decade. Aid agencies estimate that
the five-year recovery effort following the Indian Ocean tsunami cost roughly $13 billion.

Officials at the World Meteorological Organization in Geneva say record high surface temperatures in the Atlantic Ocean resulted in a huge volume of evaporated moisture entering the atmosphere and drift over the affected area. At the same time, an abnormal
airflow pattern prevented the saturated clouds from spreading over a larger area, concentrating the rains in Pakistan's watershed.

The monsoon could continue in some parts of the country for at least another three weeks. And Pakistan's chief meteorologist beliefs the floodwaters -- now covering an area larger than England -- probably won't recede until mid-September. Further
damage is expected in the southern provinces as the huge volume of water makes its way to the ocean.